1. Field of the Invention
The invention is related to chemical synthesis of nanoparticles, and more particularly, to the large-scale, safe, convenient, reproducible, energy-conserving synthesis of highly-dispersive inorganic nanoparticles with narrow size distribution.
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
Over the past decade, numerous advances have been made in the synthetic procedures for formation and isolation of high quality inorganic nanoparticles. These materials are finding applications in a wide range of disciplines, including optoelectronic devices, biological tagging, optical switching, solid-state lighting, and solar cell applications. [1-11]
One of the major hurdles for industrialization of these materials has been the development of a reproducible, high quantity synthetic methodology that is adaptable to high throughput automation for preparation of quantities of >100's of grams of single size (<5% RMS) crystalline quantum dots of various composition to be isolated. [12-13]
The general synthetic approach for preparation of colloidal semiconductor nanoparticles employs a bulky reaction flask under continuous Ar flow with a heating mantle operating in excess of 240° C. The reaction is initiated by rapid injection of the precursors, which are the source materials for the nanoparticles, at high temperatures and growth is controlled by the addition of a strongly coordinating ligand to control kinetics. And to a more limited extent, domestic microwave ovens have been used to synthesize nanoparticles. [14-19] The high temperature method imposes a limiting factor for industrial scalability and rapid nanomaterial discovery for several reasons: (1) random batch-to-batch irregularities such as temperature ramping rates and thermal instability; (2) time and cost required for preparation for each individual reaction; and (3) low product yield for device applications.
While recent advances in the field have developed better reactants, including inorganic single source precursors, metal salts, and oxides; better passivants, such as amines and non-coordinating solvents; and better reaction technologies, such as thermal flow reactors; the reactions are still limited by reproducibility. Coupled to this problem is the lack of control over reaction times, which require continuous monitoring. In the case of III-V compound semiconductors, the synthetic pathways have rates of growth on the order of days, while in the case of II-VI's, size control is very difficult and depends on the ability to rapidly cool the reaction. In these cases, the reaction depends on heating rate, heat uniformity over the reaction vessel, stirring and rapid and uniform cool-down.